Defocused laser seam stress release in flexible electrostatographic imaging member belts

ABSTRACT

A process for treating a seamed flexible electrostatographic imaging belt including providing an imaging belt having two parallel edges, the belt comprising at least one layer comprising a thermoplastic polymer matrix and a seam extending from one edge of the belt to the other, the seam having an imaginary centerline, providing an elongated support member having at arcuate supporting surface and mass, the arcuate surface having at least a substantially semicircular cross section having a radius of curvature of between about 9.5 millimeters and about 50 millimeters, supporting the seam on the arcuate surface with the region of the belt adjacent each side of the seam conforming to the arcuate supporting surface of the support member, precisely traversing the length of the seam from one edge of the belt to the other with thermal energy radiation having a narrow Gaussian wavelength distribution of between about 10.4 micrometers and about 11.2 micrometers emitted from a carbon dioxide laser, the thermal energy radiation forming a spot straddling the seam during traverse, the spot having a width of between about 3 millimeters and about 25 millimeters measured in a direction perpendicular to the imaginary centerline of the seam, and rapidly quenching the seam by thermal conduction of heat from the seam to the mass of the support member to a temperature below the glass transition temperature of the polymer matrix while the region of the belt adjacent each side of the seam conforms to the arcuate supporting surface of the support member.

BACKGROUND OF THE INVENTION

This invention relates in general to a heat treatment process and morespecifically, to a process for effective seam stress release in aflexible electrostatographic imaging member belt for improved mechanicalservice life.

Flexible electrostatographic belt imaging members are well known in theart. Typical electrostatographic flexible belt imaging members include,for example, photoreceptors for electrophotographic imaging systems,electroreceptors such as ionographic imaging members for electrographicimaging systems, and intermediate transfer belts for transferring tonerimages in electrophotographic and electrographic imaging systems. Thesebelts are usually formed by cutting a rectangular sheet from a webcontaining at least one layer of thermoplastic polymeric material,overlapping opposite ends of the sheet, and welding the overlapped endstogether to form a welded seam. The seam extends from one edge of thebelt to the opposite edge.

Flexible electrophotographic imaging member belts are usuallymultilayered photoreceptors that comprise a substrate, an electricallyconductive layer, an optional hole blocking layer, an adhesive layer, acharge generating layer, and a charge transport layer and, in someembodiments, an anti-curl backing layer. One type of multilayeredphotoreceptor comprises a layer of finely divided particles of aphotoconductive inorganic compound dispersed in an electricallyinsulating organic resin binder. A typical layered photoreceptor havingseparate charge generating (photogenerating) and charge transport layersis described in U.S. Pat. No. 4,265,990, the entire disclosure thereofbeing incorporated herein by reference. The charge generating layer iscapable of photogenerating holes and injecting the photogenerated holesinto the charge transport layer. Generally, these belts comprise atleast a supporting substrate layer and at least one imaging layercomprising thermoplastic polymeric matrix material. The "imaging layer"as employed herein is defined as the dielectric imaging layer of anelectroreceptor belt, the transfer layer of an intimidate transfer beltand the charge transport layer of an electrophotographic belt. Thus, thethermoplastic polymeric matrix material in the imaging layer is locatedin the upper portion of a cross section of an electrostatographicimaging member belt, the substrate layer being in the lower portion ofthe cross section of the electrostatographic imaging member belt.

Although excellent toner images may be obtained with multilayered beltphotoreceptors, it has been found that as more advanced, higher speedelectrophotographic copiers, duplicators and printers were developed,cracking of the charge transport layer at the welded seam area wasfrequently encountered during photoreceptor belt cycling. Seam crackinghas also been found to rapidly lead to seam delamination due to fatiguethereby shortening belt service life. Dynamic fatigue seam cracking anddelamination also occurs in ionographic imaging member belts as well.

The flexible electrostatographic imaging member belt is fabricated froma sheet cut from a web. The sheets are generally rectangular in shape.All edges may be of the same length or one pair of parallel edges may belonger than the other pair of parallel edges. The sheets are formed intoa belt by joining overlapping opposite marginal end regions of thesheet. A seam is typically produced in the overlapping marginal endregions at the point of joining. Joining may be effected by any suitablemeans. Typical joining techniques include welding (includingultrasonic), gluing, taping, pressure heat fusing, and the like.Ultrasonic welding is generally the preferred method of joining becauseis rapid, clean (no solvents) and produces a thin and narrow seam. Inaddition, ultrasonic welding is preferred because it causes generationof heat at the contiguous overlapping end marginal regions of the sheetto maximize melting of one or more layers therein.

When ultrasonically welded into a belt, the seam of multilayered imagingflexible members can crack and delaminate during extended bending andflexing over small diameter belt support rollers of an imaging machineor when subjected to lateral forces caused by rubbing contact withstationary web edge guides of a belt support module during cycling. Seamcracking and delamination is further aggravated when the belt isemployed in electrostatographic imaging systems utilizing blade cleaningdevices. Alteration of materials in the various photoreceptor beltlayers such as the conductive layer, hole blocking layer, adhesivelayer, charge generating layer, and/or charge transport layer tosuppress cracking and delamination problems is not easily accomplished.The alteration of the materials may adversely affect the overallelectrical, mechanical and other properties of the belt such as well asresidual voltage, background, dark decay, flexibility, and the like.

For example, when a flexible imaging member in an electrophotographicmachine is a photoreceptor belt fabricated by ultrasonic welding ofoverlapped opposite ends of a sheet, the ultrasonic energy transmittedto the overlapped ends melts the thermoplastic sheet components in theoverlap region to form a seam. The ultrasonic welded seam of amultilayered photoreceptor belt is relatively brittle and low instrength and toughness. The joining techniques, particularly the weldingprocess, can result in the formation of a splashing that projects outfrom either side of the seam in the overlap region of the belt. Becauseof the splashing, a typical flexible imaging member belt is about 1.6times thicker in the seam region than that of the remainder of the belt(e.g., in a typical example, 188 micrometers versus 1.6 micrometers).

The photoreceptor belt in an electrophotographic imaging apparatusundergoes bending strain as the belt is cycled over a plurality ofsupport and drive rollers. The excessive thickness of the photoreceptorbelt in the seam region due to the presence of the splashing results ina large induced bending strain as the seam travels over each roller.Generally, small diameter support rollers are highly desirable forsimple, reliable copy paper stripping systems in electrophotographicimaging apparatus utilizing a photoreceptor belt system operating in avery confined space. Unfortunately, small diameter rollers, e.g., lessthan about 0.75 inch (19 millimeters) in diameter, raise the thresholdof mechanical performance criteria to such a high level thatphotoreceptor belt seam failure can become unacceptable for multilayeredbelt photoreceptors. For example, when bending over a 19 millimeterdiameter roller, a typical photoreceptor belt seam splashing may developa 0.96 percent tensile strain due to bending. This is 1.63 times greaterthan a 0.59 percent induced bending strain that develops within the restof the photoreceptor belt. Therefore, the 0.96 percent tensile strain inthe seam splashing region of the belt represents a 63 percent increasein stress placed upon the seam splashing region of the belt.

Under dynamic fatiguing conditions, the seam provides a focal point forstress concentration and becomes the initial point of failure in themechanical integrity of the belt. Thus, the splashing tends to shortenthe mechanical life of the seam and service life of the flexible memberbelt in copiers, duplicators, and printers.

Although a solution to suppress the seam cracking/delamination problemshas been successfully demonstrated, as described in a prior art, by aspecific heat treatment process of a flexible electrophotographicimaging member belt with its seam parked directly on top of a 19 mmdiameter back support rod for stress-releasing treatment at atemperature slightly above the glass transition temperature (Tg) of thecharge transport layer of the imaging member, nevertheless this seamstress release process was also found to produce various undesirableeffects such as causing seam area imaging member set and development ofbelt ripples in the active electrophotographic imaging zones of the belt(e.g., the region beyond about 25.2 millimeters from either side fromthe midpoint of the seam). Moreover, the heat treatment can induceundesirable circumferential shrinkage of the imaging belt. The set inthe seam area of an imaging member mechanically adversely interacts withthe cleaning blade and impacts cleaning efficiency. The ripples in theimaging member belt manifest themselves as copy printout defects.Further, the heat induced imaging belt dimensional shrinkage alters theprecise dimensional specifications required for the belt. Another keyshortcoming associated with the prior art seam stress release heattreatment process is the extensive heat exposure of a large seam area.This extensive heat exposure heats both the seam area of the belt aswell as the rod supporting the seam. Since the belt must be cooled tobelow the glass transition temperature of the thermoplastic material inthe belt prior to removal from the support rod in order to produce thedesired degree of seam stress release in each belt, the heat treatmentand cooling cycle time is unduly long and leads to very high beltproduction costs.

Therefore, there is an urgent need for improving the mechanicalcharacteristics of seamed flexible imaging belts which can withstandgreater dynamic fatiguing conditions and extend belt service life freefrom any associated shortfalls.

INFORMATION DISCLOSURE STATEMENT

U.S. Pat. No. 5,240,532, issued to Yu on Aug. 31, 1993--A process fortreating a flexible electrostatographic imaging web is disclosedincluding providing a flexible base layer and a layer including athermoplastic polymer matrix comprising forming at least a segment ofthe web into an arc having a radius of curvature between about 10millimeters and about 25 millimeters measured along the inwardly facingexposed surface of the base layer, the arc having an imaginary axiswhich traversed the width of the web, heating at least the polymermatrix in the segment to at least the glass transition temperature ofthe polymer matrix, and cooling the imaging member to a temperaturebelow the glass transition temperature of the polymer matrix whilemaintaining the segment of the web in the shape of the arc.

U.S. Pat. No. 376,491 to Krumberg et al., issued Dec. 27, 1994--Anorganic photoconductor is disclosed including a base layer formed of afirst material and a photoconductive layer formed of a second material.The organic photoconductor being characterized in that when it ismaintained in a curved orientation with the photoconductive layer facingoutward, the photoconductive layer is subjected to less stress than thebase layer. In one embodiment the first material is relatively moreflexible and stretchable than said second material and the materials arepre-stressed in opposite senses. In a second embodiment the firstmaterial is relatively flexible and stretchable and the second materialis an initially less flexible and stretchable material which has beenchemically treated to increase its stretchability and flexibility.

U.S. Pat. No. 5,578,227, issued to J. Rabinovich, issued Nov. 26, 1996 Amodel making method and apparatus are disclosed which projects alinearly polarized laser beam from a laser source onto a mirror forcircularly polarizing the beam and directing the circularly polarizedbeam vertically toward a rectilinearly movable stage for fusing arectangular wire to a substrate or a previously fused wire layer on thestage. The circularly polarized beam projects through a center of aspool and a rotary stage and a support for the rotary stage and a rotaryarm which is mounted on the rotary stage. The rotary arm supports astepper feeder which draws the wire from the spool and pushes the wirethrough a nozzle, which radiuses the wire so that it lies flat andreleases the wire near a focused spot of the circularly polarized laserbeam. The rotating arm carries a lens mount on a pivot so that the lenswhich focuses the beam may traverse the wire for cutting the wire.Movement of the rectilinearly movable stage in a X-Y direction iscontrolled by a computer and stepper motors to follow a predeterminedpattern of a cross-section of the model. The rotary arm turns on therotary stage to release the wire tangentially to curvatures in the modeloutline. After each complete layer, the stage is stepped downward onewire thickness and the next layer is formed. The nozzle includes a gasjet passage for flooding the wire with inert gas as it is fused.

U.S. Pat. No. 5,021,109 to Petropoulous et al., issued Jun. 4, 1991--Aprocess is disclosed for preparing a multilayered belt comprising thesteps of: (1) heating a substrate in a form of a tubular sleeve andformed of a polymeric material to at least about a glass transitiontemperature of the polymeric material, so as to expand the tubularsleeve; (2) placing the expanded tubular sleeve on a mandrel; (3)treating the tubular sleeve by applying one or more multilayeredcomposite belts; (4) layers on the sleeve to form a heating compositebelt to at least about the glass transition temperature of the polymericmaterial of the tubular sleeve; and (5) cooling the composite belt.

U.S. Pat. No. 5,603,790 to Rhodes, issued Feb. 18, 1997--Process andapparatus for fabricating belts are disclosed. The process includesconveying the leading edge of a flexible web from a supply roll past aslitting station, slitting the web a predetermined distance from theleading edge to form a web segment having the leading edge at one endand a trailing edge at the opposite end, maintaining the web slack atthe location where the web is slit during slitting, overlapping theleading edge and the trailing edge of the web segment to form a jointand welding the joint to permanently join the leading edge and thetrailing edge together to form a belt. The apparatus includes means toconvey the leading edge of a flexible web from a supply roll past aslitting station, means at the slitting station to slit the web apredetermined distance from the leading edge to form a web segmenthaving the leading edge at one end and a trailing edge at the oppositeend, means to maintain the web slack at the location where the web isslit during slitting, means to overlap the leading edge and the trailingedge of the web segment to form a joint and means to weld the joint topermanently join the leading edge and the trailing edge together to forma belt.

U.S. Pat. No. 4,840,873 to Kobayashi et al., issued Jun. 20, 1989--Aprocess is disclosed for producing an optical recording mediumcomprising the step of heat treating an optical recording mediumcomprising a plastic substrate having a surface of minutely roughenedstructure and a thin metal film formed on the surface. The opticalrecording medium is heated at a temperature within a range which islower by 80° C. and higher by 60° C. than the glass transitiontemperature of the plastic substrate.

U.S. Pat. No. 4,532,166 to Thomsen et al., issued Jul. 30, 1985--Awelded web is disclosed which is prepared by overlapping a first edgeover a second edge, then applying heat necessary to bond the first edgewith the second edge. The heating techniques may include ultrasonicwelding, radio frequency heating, and the like.

U.S. Pat. No. 3,988,399 to Evans, issued Oct. 26, 1996--Heat recoverablearticles are disclosed which have an elongate S-shaped configuration,which later can be wrapped about a substrate. The articles comprise amolecularly oriented unitary polymeric layer which has beendifferentially annealed while restrained against dimensional change andcrosslinking.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to the following U.S. patent applications:

U.S. patent application Ser. No. 09/004289, filed on Jan. 8, 1998, inthe name of R. Yu et al., entitled "SEAM STRESS RELEASE IN FLEXIBLEELECTROSTATOGRAPHIC IMAGING BELTS", (Attorney Docket No. D/96182)--Aprocess is disclosed for treating a seamed flexible electrostatographicimaging belt including providing an imaging belt comprising at least onelayer comprising a thermoplastic polymer matrix and a seam extendingfrom one edge of the belt to the other, providing an elongated supportmember having a arcuate supporting surface and mass, the arcuate surfacehaving at least a substantially semicircular cross section having aradius of curvature of between about 9.5 millimeters and about 50millimeters, supporting the seam on the arcuate surface with the regionof the belt adjacent each side of the seam conforming to the arcuatesupporting surface of the support member with a wrap angle at leastsufficiently enough to provide arcuate support for the seam area,traversing the seam from one edge of the belt to the other with infraredrays from a tungsten halogen quartz bulb focused with a reflector havinga hemiellipsoid shape to form a heated substantially circular spotstraddling the seam during traverse, the spot having a diameter ofbetween about 3 millimeters and about 25 millimeters, without exceedingthe breadth of supported arcuate seam area, to substantiallyinstantaneously heat the thermoplastic polymer matrix in the seam andthe region of the belt adjacent each side of the seam directly under theheating spot to at least the glass transition temperature of the polymermatrix without significantly heating the support member, and rapidlyquenching the seam by thermal conduction of heat from the seam to themass of the support member to a temperature below the glass transitiontemperature of the polymer matrix while the region of the belt adjacenteach side of the seam conforms to the arcuate supporting surface of thesupport member. Apparatus for carrying out this process is alsodisclosed. The entire disclosure of this application is incorporatedherein by reference.

U.S. patent application Ser. No. 09/004290, filed on Jan. 8, 1998, inthe name of R. Yu et al., entitled "RAPID ELECTROSTATOGRAPHIC BELTTREATMENT SYSTEM", (Attorney Docket No. D/96182Q2)--A process isdisclosed for treating a seamed flexible electrostatographic imagingbelt including providing an imaging belt including at least one imaginglayer including a thermoplastic polymer matrix and a seam extending fromone edge of the belt to the other, the seam having a region on the beltadjacent each side of the seam and also having an exposed surface oneach side of the belt, supporting the belt with at least one vacuumholding device spaced from the seam while maintaining the seam andregion of the belt adjacent each side of the seam in an arcuate shapehaving at least a substantially semicircular cross section having aradius of curvature of between about 9.5 millimeters and about 50millimeters, heating the thermoplastic polymer matrix of the imaginglayer in the seam and the region of the belt adjacent each side of theseam to at least the glass transition temperature (Tg) of thethermoplastic polymer matrix without significantly heating the supportmember, and contacting the exposed surface of the seam and regions oneach side of the belt with a gas to rapidly cool the seam and regions oneach side of the belt to a temperature below the glass transitiontemperature of the polymer matrix while maintaining the arcuate shape ofthe region of the belt adjacent each side of the seam. Apparatus forcarrying out this process is also disclosed. The entire disclosure ofthis application is incorporated herein by reference.

Thus, there is a continuing need for electrostatographic imaging beltshaving improved resistance to seam cracking and delamination.

SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide animproved electrostatographic imaging belt which overcomes theabove-noted deficiencies.

It is yet another object of the present invention to provide amechanically improved seamed electrostatographic imaging belt.

It is still another object of the present invention to provide animproved electrostatographic imaging belt having an ultrasonicallywelded seam which exhibits greater resistance to cracking anddelamination.

It is another object of the present invention to provide an improvedelectrostatographic imaging belt having a welded seam which exhibitsgreater resistance to cracking and delamination and no seam area set.

It is yet another object of the present invention to provide an improvedelectrostatographic imaging belt having a welded seam which exhibitsgood dimensional tolerance.

It is also another object of the present invention to provide animproved electrostatographic imaging belt having a welded seam which isfree of belt ripple induced copy printout defects.

It is still another object of the present invention to provide animproved electrostatographic imaging belt with a stress free state inthe imaging layer around the welded seam area when theelectrostatographic imaging belt flexes over small diameter supportrollers.

The foregoing objects and others are accomplished in accordance withthis invention by providing a process for treating a seamed flexibleelectrostatographic imaging belt comprising

providing an imaging belt having two parallel edges, the belt comprising

at least one layer comprising a thermoplastic polymer matrix and

a seam extending from one edge of the belt to the other, the seam havingan imaginary centerline,

providing an elongated support member having at arcuate supportingsurface and mass, the arcuate surface having at least a substantiallysemicircular cross section having a radius of curvature of between about9.5 millimeters and about 50 millimeters, supporting the seam on thearcuate surface with the region of the belt adjacent each side of theseam conforming to the arcuate supporting surface of the support member,

precisely traversing the length of the seam from one edge of the belt tothe other with thermal energy radiation having a narrow Gaussianwavelength distribution of between about 10.4 micrometers and about 11.2micrometers emitted from a carbon dioxide laser, the thermal energyradiation forming a spot straddling the seam during traverse, the spothaving a width of between about 3 millimeters and about 25 millimetersmeasured in a direction perpendicular to the imaginary centerline of theseam, and

rapidly quenching the seam by thermal conduction of heat from the seamto the mass of the support member to a temperature below the glasstransition temperature of the polymer matrix while the region of thebelt adjacent each side of the seam conforms to the arcuate supportingsurface of the support member.

Although this invention relates to mechanical improvements ofelectrostatographic imaging member belts, the following will focus onelectrophotographic imaging belts to simplify discussion.

A more complete understanding of the process of the present inventioncan be obtained by reference to the accompanying drawings wherein:

BRIEF DESCRIPTION OF THE DRAWINGS

In the detailed description of the preferred embodiment of the presentinvention, reference is made to the accompanying drawings, in which:

FIG. 1 is a cross-sectional view of a multiple layered flexible sheet ofelectrophotographic imaging material with opposite ends overlapped.

FIG. 2 is a cross-sectional view of a multiple layered seamed flexibleelectrophotographic imaging belt derived from the sheet of FIG. 1 afterultrasonic seaming welding.

FIG. 3 is a schematic, elevational view of an ultrasonic weldingapparatus.

FIG. 4 is a cross-sectional view of a multiple layered seamed flexibleelectrophotographic imaging belt which has failed due to seam crackingand delamination.

FIG. 5 is an isometric schematic view of a seamed flexibleelectrophotographic imaging belt in which the belt seam is positionedover a cylindrical tube, the belt being tensioned by the weight of asecond cylindrical tube for seam heat treatment in accordance with priorart processing.

FIG. 6 is an isometric schematic view of a seamed flexibleelectrophotographic imaging member belt in which the seam is parked onand held against the arcuate surface of an elongated support member byvacuum while subjected to the seam stress-release process of the presentinvention.

FIG. 7 is a schematic, cross-sectional view of a carriage carrying awelded belt seam parallel to and spaced from a carbon dioxide laser.

FIG. 8 is a partial schematic plan view of the carriage shown in FIG. 7.

In the drawings and the following description, it is to be understoodthat like numeric designations refer to components of like function.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Although specific terms are used in the following description for thesake of clarity, these terms are intended to refer only to theparticular structure of the invention selected for illustration in thedrawings, and are not intended to define or limit the scope of theinvention.

Referring to FIG. 1, there is illustrated a flexible member 10 in theform of a sheet having a first end marginal region 12 overlapping asecond end marginal region 14 to form an overlap region ready for a seamforming operation. The flexible member 10 can be utilized within anelectrophotographic imaging device and may be a single film substratemember or a member having a film substrate layer combined with one ormore additional coating layers. At least one of the coating layerscomprises a film forming binder.

The flexible member 10 may be a single layer or comprise multiplelayers. If the flexible member 10 is to be a negatively chargedphotoreceptor device, the flexible member 10 may comprise a chargegenerator layer sandwiched between a conductive surface and a chargetransport layer. Alternatively, if the flexible member 10 is to be apositively charged photoreceptor device, the flexible member 10 maycomprise a charge transport layer sandwiched between a conductivesurface and a charge generator layer.

The layers of the flexible member 10 can comprise numerous suitablematerials having suitable mechanical properties. Examples of typicallayers are described in U.S. Pat. Nos. 4,786,570, 4,937,117 and5,021,309, the entire disclosures thereof being incorporated herein byreference. The belt or flexible member 10 shown in FIG. 1, includingeach end marginal region 13 and 14, comprises from top to bottom acharge transport layer 16 (e.g., 24 micrometers thick), a generatorlayer 18 (e.g., 1 micrometer thick), an interface layer 20 (e.g., 0.05micrometer thick), a blocking layer 22 (e.g., 0.04 micrometer thick), aconductive ground plane layer 24 (e.g., 0.02 micrometer thick, asupporting layer 26 (e.g., 76.2 micrometer thick), and an anti-curl backcoating layer 28 (e.g., 14 micrometer thick). It should be understoodthat the thickness of the layers are for purposes of illustration onlyand that a wide range of thicknesses can be used for each of the layers.

The end marginal regions 12 and 14 can be joined by any suitable meansincluding gluing, taping, stapling, pressure and heat fusing to form acontinuous member such as a belt, sleeve, or cylinder. Preferably, bothheat and pressure are used to bond the end marginal regions 12 and 14into a seam 30 in the overlap region as illustrated in FIG. 2. Asillustrated in FIG. 2, the location of seam 30 is indicated by a dottedline. Seam 30 comprises two vertical portions joined by a horizontalportion. Thus, the midpoint of seam 30 may be represented by animaginary centerline extending the length of seam 30 from one edge ofbelt 10 to the opposite edge, the imaginary centerline (not shown)running along the middle of the horizontal portion which joins the twovertical portions illustrated in FIG. 2. In other words, a plan view(not shown) of the horizontal portion of seam 30 would show a strip muchlike a two lane highway in which the centerline would be represented bythe white divider line separating the two lanes. The flexible member 10is thus transformed from a sheet of electrophotographic imaging materialas illustrated in FIG. 1 into a continuous electrophotographic imagingbelt as illustrated in FIG. 2. The flexible member 10 has a first majorexterior surface or side 32 and a second major exterior surface or side34 on the opposite side. The seam 30 joins the flexible member 10 sothat the bottom surface 34 (generally including at least one layerimmediately above) at and/or near the first end marginal region 12 isintegral with the top surface 32 (generally including at east one layerimmediately below) at and/or near the second end marginal region 14.

A preferred heat and pressure joining means includes ultrasonic weldingto transform the sheet of photoconductive imaging material into aphotoreceptor belt. The belt can be fabricated by ultrasonic welding ofthe overlapped opposite end regions of a sheet. In the ultrasonic seamwelding process, ultrasonic energy applied to the overlap region is usedto melt suitable layers such as the charge transport layer 16, generatorlayer 18, interface layer 20, blocking layer 22, part of the supportlayer 26 and/or anti-curl back coating layer 28. Direct fusing of thesupport layer achieves optimum seam strength.

A conventional ultrasonic welding apparatus 36 is shown in FIG. 3. Theapparatus 36 comprises an ultrasonic horn 38 which is caused tooscillate along its longitudinal axis by a transducer assembly 40affixed to the top thereof. A solenoid 42 is mounted above thetransducer assembly 40 to extend or retract the ultrasonic horn 38 andthe transducer assembly 40 in the vertical direction. The seam 30, (notshown in FIG. 3) formed by the overlapping segment end marginal regions12 and 14 of the flexible member 10, is supported by the upper surfaceof anvil 44 and held in place below the path of the ultrasonic horn 38by suction from parallel rows of grooves 46, 48, 50 and 52. The anvil 44preferably includes or is connected to a vacuum source for holding downoverlapping ends of member 10. The ultrasonic horn 38 and the transducerassembly 40 are supported by the lower end of a vertically reciprocatingshaft (not shown) extending from the lower end of the solenoid 42mounted to the upper hinged half of a substantially horizontallyreciprocating carriage 54. One side of the lower hinged half of thecarriage 54 is suspended from a pair of pillow blocks 56 which, in turn,slides on a horizontal bar 58. The other side of carriage 54 issuspended from a pair of cam followers 60 that rolls on the outersurface of a horizontal bar 62. A rotatable lead screw 64 drives thehorizontally reciprocating carriage 54 through a ball screw 66 securedto the carriage 54. The horizontal bars 58 and 62, as well as the leadscrew 64, are secured at each end by a frame assembly (not shown). Thelead screw 64 is rotated by a belt driven by an electric motor (notshown) which is also supported by the frame assembly.

When the overlap region formed by the end marginal regions 12 and 14 ofthe flexible member 10, is positioned on the anvil 44 below theultrasonic horn 38 at a belt welding station, the solenoid 42 isinactivated to extend the transducer 40 toward the anvil 44 from aretracted position (in which the solenoid 42 is activated). Thetransducer 40 is activated by the electric motor to drive the lead screw64 which, in turn, moves the horizontally reciprocating carriage 54 overthe seam 30 supported by the anvil 44.

Lowering of the transducer 40 by inactivation of solenoid 42 brings theultrasonic horn 38 into compressive engagement with an appropriateoverlap region, e.g., 0.040 inch of the flexible member 10. The highvibration frequency of the ultrasonic horn 38 along its vertical axiscauses the temperature of at least the contiguous overlapping surfacesof the flexible member 10 to increase until at least one layer (e.g.,charge transport layer 16) of the flexible member 10 flows, resulting inthe formation of a welded seam 30. Welding of the contiguous overlappingsurfaces of the flexible member 10 can best be accomplished if theflexible member 10 comprises layers which flow as a result of theapplied energy of ultrasonic oscillations (e.g., charge transport layer16 and anti-curl back coating layer 28). For optimum seam strength, itis preferable that the layers of the flexible member 10 at the overlapregion be brought to the melting stage by the applied ultrasonic energy.In this manner, fusing of support layer 26 can be achieved to form thewelded seam 30 as illustrated in FIG. 2. Welding of opposite ends of asheet to form an electrophotographic belt is well known and described,for example, in U.S. Pat. Nos. 4,838,964, 4,878,985, 5,085,719 and5,603,790, the entire disclosures thereof being incorporated herein byreference.

The flexible member 10 may be of any suitable thickness which will allowadequate heating of the contiguous overlapping surfaces of the endmarginal regions 12 and 14 to cause joining when sufficient heat energyto be applied to the contiguous overlapping surfaces. Any suitableheating technique may be used to provide the heat necessary at thecontiguous overlapping surfaces to melt the thermoplastic material andcause it to weld the overlap region of the flexible member 10. Thus, asuitable technique permanently transforms the form of the flexiblemember 10 from a sheet of electrophotographic imaging material into anelectrophotographic imaging belt.

When ultrasonic welding is utilized at the contiguous overlappingregion, the flexible member 10 is positioned between the anvil 44 andultrasonic horn 38. The rapid impact of the first end marginal region 12against the second end marginal region 14 of the flexible member 10causes generation of heat. A horn vibration frequency from a range ofabout 16 KHz or higher may be utilized to cause the flexible member 10to soften and melt. Since heat is generated very rapidly at theinterface of the device, sufficient heat to cause the layers of theflexible member 10 to melt can occur typically in about 1.2 seconds asthe horn 38 traverses along the overlap region.

As the horn 38 is lowered to the overlap region of the flexible member10, electrical power is supplied to the transducer 40 and the electricmotor (not shown) is activated to drive the lead screw 64 which, inturn, moves the horizontally reciprocating carriage 54 and ultrasonichorn 38 along the overlap region of the flexible member 10. After thecarriage 54 completes its traversal of the overlap region, the solenoid42 is activated to retract the transducer 40 away from anvil 44, thetransducer 40 is inactivated, and the electric motor (not shown) isreversed to return the horizontally reciprocating carriage 54 to itsstarting position. A typical ultrasonic horn traverse speed for theseaming operation can be selected in a range from 1 to 5 inches persecond.

Upon completion of the welding of the overlap region into a seam 30, theoverlap region is transformed into an overlapping and abutting region asillustrated in FIGS. 2 and 4. Within the overlapping and abuttingregion, the portions of the flexible member 10, which once formed theend marginal regions 12 and 14, are joined by the seam 30 such that theonce end marginal regions 12 and 14 are overlapping and abutting oneanother. The welded seam 30 contains upper and lower splashings 68 and70 at each end thereof as illustrated in FIGS. 2 and 4. The splashings68 and 70 are formed in the process of joining the end marginal regions12 and 14 together. Molten material is necessarily ejected from eitherside of the overlap region to facilitate direct support layer 26 tosupport layer fusing and results in the formation of the splashings 68and 70. The upper splashing 68 is formed and positioned above theoverlapping end marginal region 14 abutting the top surface 32 andadjacent to and abutting the overlapping end marginal region 12. Thelower splashing 70 is formed and positioned below the overlapping endmarginal region 12 abutting bottom surface 34 and adjacent to andabutting the overlapping end marginal region 14. The splashings 68 and70 extend beyond the sides and the edges of the seam 30 in the overlapregion of the welded flexible member 10. The extension of the splashings68 and 70 beyond the sides and the edges of the seam 30 is undesirablefor many machines such as electrophotographic copiers, duplicators andcopiers that require precise edge positioning of a flexible member 10during machine operation. Generally, the extension of the splashings 68and 70 at the belt edges of the flexible member 10 are removed by anotching operation.

A typical splashing has a thickness of about 68 micrometers. Each of thesplashings 68 and 70 has an uneven but generally rectangular shapeincluding one side (free side) 72 (which forms a free end) extendinginwardly from an outwardly facing side 74 (extending generally parallelto either the top surface 32 or the bottom surface 34). The free side 72of the splashing 68 forms an approximately perpendicular angle θ₁ withthe bottom surface 34 of the flexible member 10. Likewise, the free side72 of the splashing 70 forms an approximately perpendicular angle θ₂meeting or junction point 76 exists at the junction of the free side 72of the upper splashing 68 and the top surface 32 of the flexible member10. Likewise, a meeting or junction point 78 exists at the junction ofthe free side 72 of the lower splashing 70 and the bottom surface 34 ofthe flexible member 10. Both junction points 76 and 78 provide focalpoints for the stress concentration and become the initial points offailure affecting the mechanical integrity of the flexible member 10.

During machine operation, the seamed belt flexible member 10 cycles orbends over rollers, particularly small diameter rollers, of a beltsupport module within an electrophotographic imaging apparatus. In thiscase, as a result of dynamic bending of the flexible member 10 duringdynamic cycling, the rollers exert a force on the flexible member 10which causes large stress to develop generally adjacent to the seam 30due to the excessive thickness thereof. The stress concentrations thatare induced by bending near the junction points 76 and 78 may reachvalues much larger than the average value of the stress over the entirelength of the flexible member 10. The induced bending stress isinversely related to the diameters of a roller that the flexible member10 bends over and directly related to the thickness of the seam 30 ofthe flexible member 10. When a structural member, such as the flexiblemember 10, contains a sudden increase in cross-sectional thickness atthe overlap region, high localized stress occurs near the discontinuity,e.g., junction points 76 and 78.

When the flexible member 10 bends over the rollers of a belt modulewithin an electrophotographic imaging apparatus, the bottom surface 34of the flexible member 10, which is adapted to contact the exteriorsurface of the roller, is compressed. In contrast, the top surface 32 isstretched under tension. This is attributable to the fact that the topsurface 32 and bottom surface 34 move in a circular path about thecircular roller. Since the top surface 32 is at greater radial distancefrom the center of the circular roller than the bottom surface 34, thetop surface 32 must travel a greater distance than the bottom surface 34in the same time period. Therefore, the top surface 32 must be stretchedunder tension relative to a generally central portion of the flexiblemember 10 (the portion of the flexible member 10 generally extendingalong the center of gravity of the flexible member 10). Likewise, thebottom surface 34 must be compressed relative to the generally centralportion of the flexible member 10 (the portion of the flexible member 10generally extending along the center of gravity of the flexible member10). Consequently, the bending stress at the junction point 76 will betension stress, and the bending stress at the junction point 78 will becompression stress.

Compression stresses, such as at the junction point 78, rarely causeseam 30 failure. Tension stresses, such as at junction point 76,however, are much more of a problem. The tension stress concentration atthe junction point 76 in great likelihood will eventually result incrack initiation through the electrically active layers of the flexiblemember 10 as illustrated in FIG. 4. The illustrated crack 80 is adjacentto the top splashing 68 of the second end marginal region 14 of theflexible member 10. The generally vertically extending crack 80initiated in the charge transport layer 16 continues to propagatethrough the generator layer 18. Inevitably, the crack 80 extendsgenerally horizontally to develop seam delamination 81 which ispropagated through the relatively weak adhesion bond between theadjoining surfaces of the generator layer 18 and the interface layer 20.

The formation of the local seam delamination 81 is typically referred toas seam puffing. The effect of the excess thickness of the splashing 68and stress concentration at the junction point 76 is to cause theflexible member 10 to perform, during extended machine operation, as ifa material defect existed therein. Thus, the splashing 68 tends topromote the development of dynamic fatigue seam 30 failure and can leadto separation of the joined end marginal regions 12 and 14 severing theflexible member 10. Consequently, the service life of the flexiblemember 10 is shortened.

In addition to seam failure, the crack 80 acts as a depository site andcollects toner, paper fibers, dirt, debris and other unwanted materialsduring electrophotographic imaging and cleaning of the flexible member10. For example, during the cleaning process, a cleaning instrument,such as a cleaning blade, will repeatedly pass over the crack 80. As thesite of the crack 80 becomes filled with debris, the cleaning instrumentdislodges at least some portion of this highly concentrated level ofdebris from the crack 80. The amount of the debris, however, is beyondthe removal capacity of the cleaning instrument. As a consequence, thecleaning instrument dislodges the highly concentrated level of debrisbut cannot remove the entire amount during the cleaning process.Instead, portions of the highly concentrated debris is deposited ontothe surface of the flexible member 10. In effect, the cleaninginstrument spreads the debris across the surface of the flexible member10 instead of removing the debris therefrom.

In addition to seam failure and debris spreading, the portion of theflexible member 10 above the seam delamination 81, in effect, becomes aflap which moves upwardly. The upward movement of the flap presents anadditional problem during the cleaning operation. The flap becomes anobstacle in the path of the cleaning instrument as the instrumenttravels across the surface of the flexible member 10. The cleaninginstrument eventually strikes the flap when the flap extends upwardly.As the cleaning instrument strikes the flap, great force is exerted onthe cleaning instrument which can lead to damage thereof, e.g.,excessive wear and tearing of the cleaning blade.

In addition to damaging the cleaning blade, the striking of the flap bythe cleaning instrument causes unwanted vibration in the flexible member10. This unwanted vibration adversely affects the copy/print qualityproduced by the flexible member 10. The copy/print is affected becauseimaging occurs on one part of the flexible member 10 simultaneously withthe cleaning of another part of the flexible member 10.

Vibration problems encountered with the flexible member 10 is notexclusively limited to a flexible member 10 undergoing seam delamination81. The discontinuity in cross-sectional thickness of the flexiblemember 10 at junction points 76 and 78 also can also create unwantedvibration, particularly when the flexible member 10 bends over smalldiameter rollers of a belt module or between two closely adjacentrollers.

Illustrated in FIG. 5 is a belt 10 mounted directly on a supportingcylindrical tube 90 having an outer radius of curvature between about9.5 millimeters and about 50 millimeters (i.e. diameter of curvature ofbetween about 19 millimeters and about 100 millimeters). When thediameter of curvature chosen for seam heat treatment is less than about9.5 millimeters (i.e. diameter of curvature of about 19 millimeters),the beam rigidity of the electrophotographic imaging belt will renderextremely difficult any effort to bending of the belt 10 to achieve avery small curvature prior to heat treatment. When the radius ofcurvature is greater than about 50 millimeters (i.e. diameter ofcurvature of about 100 micrometers), the benefits of the presentinvention are not fully realized because no significant seam stressrelease in the imaging layer is achieved. As shown in FIG. 5, theelectrophotographic imaging belt 10 may be positioned with belt seam 30parked directly over supporting cylindrical tube 90, the arcuate surfaceof tube 90 being in intimate contact with the back surface of belt 10and the imaging surface of belt 10 facing outwardly away from tube 90.To ensure intimate contact and conformance of the belt with about halfof the tube 90, a slight tension is applied to the belt 10 by insertinga light weight cylindrical tube 92 inside the lower loop of belt 10while the belt 10 is hanging from tube 90. Tube 90 may be cantileveredby securing one end to a supporting wall or frame. The radius ofcurvature of tube 90 can vary from about 9.5 millimeters to any largerdimension of about 50 millimeters. A desirable wrapped angle for theseam segment parking over the back supporting cylindrical tube 90 shouldprovide an arcuate area at the seam region at least about as wide as theincident laser beam spot. It is preferred that the wrap angleencompassing the seam and region of the belt adjacent each side of theseam conforming to the arcuate supporting surface of the support memberbe between about 10 degrees and about 180 degrees. The material used fortube 90 and tube 92 may be of any suitable material, including forexample, metal, plastic, composites, and the like. With the schematicarrangement described in FIG. 5, a heating element or source (not shown)is positioned directly above the supporting cylindrical tube 90 toprovide heat energy for the seam stress release heat treatment process.Since the heating means employed in prior art seam heat treatmentprocesses are usually a hot air impingement source, a toaster oven typeheater comprising hot wire filaments or a quartz tube, since the entireseam length area directly under heat exposure is large, and since thebelt support member underlying the seam has mass, a lengthy time isrequired for the seam area to reach the seam stress release temperatureand a long time is required for cooling of the seam area and beltsupport member. Moreover, the typical heat source used for the prior artseam heat treatment process emits a broad band of infrared radiant heatwhich requires several minutes of elapsed time to complete aheating/cooling processing cycle. These prior approaches caused heatingof the supporting cylindrical member which retarded cooling rates forbelt after heating. Furthermore, if a heat source were a laser, thereare a vast number of different kinds of lasers, some of which areunsuitable and some which may perform poorly. For example, there arefrequency doubled lasers, rare gas lasers such as an argon laser,argon/krypton laser, neon laser, helium neon laser, xenon laser andkrypton laser, carbon monoxide laser, carbon dioxide laser, metal ionlasers such as cadmium ion laser, zinc ion laser, mercury ion laser andselenium ion laser, lead salt laser, metal vapor lasers such as coppervapor laser and gold vapor laser, nitrogen laser, ruby laser, iodiumlaser, neodymium glass laser, neodymium YAG laser, KTP laser, dye laserssuch as a dye laser employing Rhodamine 640, Kitom Red 620 or Rhodamine590 Dye, doped fiber laser, and the like. Different lasers producedramatically different results. Thus, for example, when a green laserhaving a 532 nanometers wavelength is employed, the desired seam stressrelease is not obtained and imaging member discoloration is observed.Similarly, when a neodymium YAG laser having a wavelength of 1.06micrometers is used, ineffective seam stress release is encounteredbecause the radiant energy absorbed causes material ablation which, inturn, adversely alters the crucially important physical integrity of theseam. Other lasers, such as the excimer laser using rare gas halides,emits ultraviolet radiation which is deemed unsuitable for the seamtreatment purpose because it does not provide thermal energy at all toeffect seam stress release but rather causes material excitation leadingto fragmentation of polymer chains and vaporization of seam material.Argon lasers emit radiation having a wavelength between 400 nanometersto 500 nanometer.

In sharp contrast, the process of the present invention, as illustratedin FIG. 6, utilizes a sealed carbon dioxide laser 103 to providelocalized heating of only a small substantially circular spot straddlingthe seam 30 while the seam of imaging member belt 10 is parked at aboutthe 12 o'clock position of a hollow support tube 90. Instead of a weightcylinder 92 (see FIG. 5) to provide belt tension, a narrow slot 104[e.g. having a width of about 0.06 inch (1.5 millimeters)] is used oneach side of the hollow support tube 90 to hold the belt 10 against thearcuate surface of tube 90. The slots 104 are about 180 degrees apartand extend axially along each side of tube 90. One end of tube 90 issealed (not shown) and the other is connected by a suitable device suchas a valved flexible hose (not shown) to any suitable vacuum source.After belt 10 is placed on tube 90 manually or by any suitableconventional robotic device, the initially closed valve on the flexiblehose to the vacuum source is opened to suck belt 10 against the upperarcuate semicircular surface of tube 90 and to achieve a substantially180 degree wrap of belt 10 around the upper arcuate semicircular surfaceof tube 90. Plugs, seals, end-caps, or the like may be used to close theend openings of supporting tube 90 to ensure vacuum buildup. If desired,a plurality of holes of any suitable shape (e.g. round, oval, square,and the like) may be used instead of or in addition to the slots 104.The size of the slots and holes should be small enough to avoiddistortion of the belt during the heating and cooling steps. Theresistance of the belt to distortion when suction is applied depends onthe beam strength of the specific belt employed which in turn dependsupon the specific materials in and thickness of the layers in the belt.The sealed carbon dioxide laser 103 emits a narrow Gaussian distributionwavelength between about 10.4 micrometers and about 11.2 micrometers.The peak radiant energy wavelength emitted by the sealed carbon dioxidelaser 103 is about 10.64 micrometers. Generally, pulse type radiation ispreferred over continuous wave irradiation because delivery of a seriesof pulses provides an addition control over the interaction absorptionof radiation and the overall process. This leads to more control of theheating and the degree of damage to the layer materials. The combinationof using a power density of from about 0.01 watt per square millimeterto about 0.71 watt per square millimeter, a pulse duration between about30 microseconds and about 150 microseconds, and a frequency range fromabout 50 hertz to about 200 hertz gives satisfactory seam stress releaseheat treatment results without melting, vaporization or cutting throughof the seam components during the heat treatment. The specificcombination utilized depends upon the specific materials being heatedand the relative rate of traverse. Sealed carbon dioxide (CO₂) lasersare commercially available. A typical commercially available highpowered sealed carbon dioxide laser heating source is a Model Diamond 64sealed carbon dioxide laser from Coherent, Inc. which is a slab lasercomprising a pair of spaced apart, planar electrodes having opposedlight reflecting surfaces. The spacing of the electrodes is arrangedsuch that light will be guided in a plane perpendicular to thereflecting surfaces. In contrast, the light in the plane parallel to thelight reflecting surfaces is allowed to propagate in free space and isonly confined by a resonator. Preferably, the lasing medium is standardCO₂ lasing mixture including helium, nitrogen and carbon dioxide with a3:1:1 ratio plus the addition of five per cent xenon. The gas ismaintained between 50 and 110 torr and preferably on the order of about80 torr. The gas is electrically excited by coupling a radio frequencygenerator between the electrodes. A typical sealed carbon dioxide laseris described, for example, in U.S. Pat. No. 5,123,028, the entiredisclosure thereof being incorporated herein by reference. Sealed carbondioxide lasers are also described in U.S. Pat. Nos. 5,353,297, 5,353,297and 5,578,227, the entire disclosures thereof also being incorporatedherein by reference. Although this sealed carbon dioxide laser has a 150watt capability, it is adjusted to only deliver a lower output of, forexample, about 6 watts for the seam heat treatment process of thisinvention. A phase shift mirror may be used to transform a laser beamwith linear polarization into a beam with circular polarization. Toobtain a circularly polarized beam a phase shift mirror is positionedwith an incidence angle of 45 degrees and the laser beam output with aplane of polarization parallel to the laser base is rotated 45 degreesto the plane of incidence. The resulting circularly polarized beam isfocused with an image lens into a desired size small spot on the outersurface of the seam. A Melles Griot Zinc Selenide Positive Lens withfocal distance 63.5 mm (2.5 inches) may be used as the image lens. Inthe process of the present invention, all of the radiant energy spotemission from the carbon dioxide laser 103 strikes the seam and regionsof the imaging belt immediately adjacent the seam to deliver instantheating and quick cooling as the belt 10 with the supporting cylindrical90 traverses under the laser heating source.

Generally the raw laser beam emitted from a laser has a circular crosssection. The diameter of a raw beam emitted by a laser is normallyconstant along the entire length of the beam. The thermal energyradiation emitted from a carbon dioxide laser is directed at the seam ofthe belt and the thermal energy radiation from the laser forms a spotstraddling the seam during traverse of the seam. The spot on the surfaceof the seam preferably has a width of between about 3 millimeters andabout 25 millimeters measured in a direction perpendicular to theimaginary centerline of the seam. For example, the Model Diamond 64sealed carbon dioxide laser from Coherent, Inc. has a circular raw beamhaving a diameter of about 6 millimeters. This raw laser beam will forma spot having a diameter of about 6 millimeters on the belt seam. Ifdesired, the 6 millimeter spot size of the thermal energy striking theouter surface of the seam can be reduced for small seam area heatexposure by masking the emitted raw laser beam using any suitable devicesuch as a metal template, to give a 3 millimeter to 6 millimeter heatspot size measured in a direction perpendicular to the imaginarycenterline of the seam. Although the template may alter the spot shapeto any suitable and desired shape such as an oval, square, rectangle andthe like, a spot having a circular spot is preferred. Moreover, wherefor example, the laser beam has a diameter of about 6 millimeter in alarger heat spot is desired on the outer surface of the belt seam, thelaser beam may be defocused using any suitable device such as a zincselenide lens between the laser beam source and the belt seam. Thus, byvarying the relative distances between the laser beam source, the lensand the belt seam, the 6 millimeter diameter laser beam may be defocusedto give a larger spot having a diameter greater than about 6 millimetersand preferably less than about 25 millimeters in diameter measured in adirection perpendicular to the imaginary centerline of the seam forstress release treatment of large seam areas. If a mask is employed tochange the shape of the raw laser beam or the defocused beam to form aspot shape other than round, the preferred spot size that straddles theseam is between about 3 millimeters and about 25 millimeters measured ina direction perpendicular to the imaginary centerline of the seam. Sincethe carbon dioxide laser delivers constant diameter raw beam, thephysical distance from the seam surface of the imaging belt to the laseris not critical for the heat treatment process of this invention, if theintended seam heat treatment spot size is the same as the diameter ofthe raw laser beam or smaller than the raw laser beam by using a maskingtemplate. The carbon dioxide laser spot substantially instantaneouslyelevates the temperature of only a small localized region of the imaginglayer of the imaging member belt, which is in the upper portion of theseam area, above the glass transition temperature (Tg). Typically, theTg of a film forming polymer used for electrostatographic imaging layercoating applications is at least about 45° C. to satisfy most imagingbelt machine operating conditions. Preferably, the heat treatment iscarried out between about the Tg and about 25° C. above the Tg of theimaging layer to achieve sufficient seam stress release. Melting,vaporization or cutting through of the seam components during heattreatment should be avoided.

Because of its bulk and weight, the carbon dioxide laser 103 ispreferably stationary during treatment of the belt seam. Thus, tube 90bearing belt 10 and seam 30 are moved substantially continuously orincrementally under carbon dioxide laser 103 manually or automaticallysuch as by any suitable horizontally reciprocateable carriage system(not shown). Alternatively, the tube 90 bearing belt 10 and seam 30 maybe held stationary and the carbon dioxide laser 103 maybe movedsubstantially continuously or incrementally either manually orautomatically such as by any suitable horizontally reciprocateablecarriage system (not shown). The horizontally reciprocateable carriagesystem may be driven by any suitable device such as a lead screw andmotor combination, belt or chain drive slide system, and the like. Asuitable horizontally reciprocateable carriage, lead screw and motorcombination is described with reference to FIGS. 7 and 8 and the weldingsystem illustrated in FIG. 3. Thus, for example, the heating source 103shown in FIG. 6 may be mounted on the horizontally reciprocatingcarriage 54 illustrated in FIG. 3 instead of the ultrasonic weldingapparatus 36 shown in FIG. 3. Conversely, the cylindrical support memberand belt may be mounted on the horizontally reciprocating carriage 54illustrated in FIG. 3 instead of the ultrasonic welding apparatus 36shown in FIG. 3. Similar suitable horizontally reciprocateable carriage,lead screw and motor combinations are described in U.S. Pat. Nos.4,838,964, 4,878,985, 5,085,719 and 5,603,790, the entire disclosuresthereof being incorporated herein by reference. If desired, both theheating source and belt with support member may simultaneously be movedto achieve relative movement between each other. The heating source 103is preferably transported across the width of the belt directly over theentire length of the seam 30 at a speed between about 1 inch (2.54centimeters) and about 5 inches (12.7 centimeters) per second.

For heat treatment of a flexible imaging member belt having a slantedseam, the heating source may be set to precisely track the seam whentraversing the entire belt width. However, it is preferred that the beltis cocked and adjusted such that the seam is positioned without skewingalong the top of the support cylindrical tube after belt mounting.

Illustrated in FIGS. 7 and 8 is a substantially horizontallyreciprocating carriage 110. One side of the lower half of the carriage110 is suspended from a pair of pillow blocks 112 which, in turn, slideson a horizontal bar 114. The other side of carriage 110 is suspendedfrom a pair of cam followers 116 that rolls on the outer surface of ahorizontal bar 118. A rotatable lead screw 120 drives the horizontallyreciprocating carriage 110 through a ball screw 122 secured to thecarriage 110. The horizontal bars 114 and 118, as well as the lead screw120, are secure at each end by a frame assembly 124. The lead screw 120is rotated by a belt driven by an electric motor 126 which is alsosupported by the frame assembly 124.

Wall 128 at one end of carriage 110, supports one end of cantileveredhollow support tube 90. Belt 10 is held in intimate contact,with theupper arcuate semicircular surface of tube 90 by suction from vacuumslits 104 (see FIG. 6). a vacuum is supplied to hollow tube 90 throughfitting 136 and flexible hose 138. Flexible hose 138 is connectedthrough any suitable manually or electrically activateable valves (notshown) to any suitable vacuum source such as a vacuum tank or vacuumpump (not shown). If desired, a pin stop (not shown) may be installed atthe top of tube 90 near the cantilevered end to help position belt 10 ontube 90 prior to opening the valve to the vacuum source. Horizontalmovement of the reciprocating carriage 110 is accomplished by activationof electric motor 126 to drive the lead screw 120 which, in turn, movesthe horizontally reciprocating carriage 110, tube 90, belt 10 and seam30 under stationary laser 103. A single pass of reciprocating carriage110, tube 90, belt 10 and seam 30 under stationary laser 103 is normallysufficient to achieve stress reduction in the seam area of belt 10.After heat treatment, electric motor 126 is reversed to return thehorizontally reciprocating carriage 110 to its starting position.Conventional electrical switching is employed to couple, uncouple orreverse electric motor 126 with an electrical power source throughsuitable circuitry in response to a signal from a suitable programmablecontroller 56 such as a Allen Bradley Programmable Controller, Model No.2/05 or Model No. 2/17. If desired, the free end of support member 90may be supported by any suitable mechanism to minimize movement duringany stage of belt treatment. For example, a pin may be used to supportthe end of support member 90 after belt 10 has been mounted on member90. The use of pins is disclosed, for example, in U.S. Pat. Nos.4,838,964, 4,878,985 and 5,085,719, the entire disclosures thereof beingincorporated herein by reference.

Since the high intensity infrared spot focused on the surface of seam 30substantially instantaneously elevates the temperature of only a smalllocalized region of the imaging layer, which is in the upper portion ofthe seam, and regions of the belt immediately adjacent the seam abovethe glass transition temperature, the temperature of the underlyingsupport tube 90 remains substantially unaffected under the seam area andmore rapid cooling of the heat treated seam can be achieved subsequentto heating. The instant seam heating of a very small area heat sourcetraversal of the seam and rapid cooling are key features which allow thelarge mass of the back supporting cylinder 90 to serve as a heat sinkwhich quickly quenches the hot seam spot back to room ambienttemperature as the heat source is transporting across the entire beltwidth. With this fast seam heating/cooling combination, the seam stressrelease heat treatment operation cycle time can be accomplished in amatter of seconds, depending on the belt width of an electrophotographicimaging belt product. This extremely brief treatment cycle time is ofcrucial importance because it can be integrated into a high volumeproduction process and function synchronously with high speed ultrasonicseam welding operations without adversely impacting beltfabrication/finishing throughput. Furthermore, the process of thisinvention effectively suppresses heat induced belt circumferentialshrinkage and localized seam area set as well as the formation ofripples in the leading and trailing edges of the imaging zones near theseam, typically associated with prior art welded seam belts.

For belts having a seam extending perpendicular to the parallel edges ofthe belt, the path of the moving seam 30 can be readily transported toprecisely track under the beam of carbon dioxide laser 103 until theentire length of seam 30 has been treated. The entire length of seam 30is located at the top (12 o'clock position) of the back supporting tube90. However, for skewed seam belts where the seam is not perpendicularto the parallel edges of the belt, only the mid point of the entire seamlength would normally be located at the top (12 o'clock position) of theback supporting cylinder 90 when the parallel edges of the belt arearranged perpendicular to the axis of the supporting cylinder 90. Thus,it is preferred to cock the edges of the belt to so that the entire seamlength 30 is positioned and parked directly along the top of the backsupporting tube 90 prior to heat treatment of the seam.

The seam stress release heat treatment process of this invention isdesigned for high speed processing. The treating of the flexibleelectrostatographic imaging belt 10 described above and in the WorkingExamples below comprises bending the short segment of theelectrostatographic imaging belt into an arc having an a substantiallysemicircular cross section and an imaginary axis which transverses thewidth of the belt with the seam situated at the middle of the arc. Thedesired arc may be conveniently formed by parking the flexibleelectrostatographic imaging belt 10 on the arcuate surface of anelongated support member, the arcuate surface having at least asubstantially semicircular cross section having a radius of curvature ofbetween about 9.5 millimeters and about 50 millimeters. The elongatedsupporting member may simply be a solid or hollow tube or bar. Since thebelt 10 need only contact the arcuate surface, the remaining surface ofthe elongated supporting member may be of any other suitable shape. Forexample, a bar having a rectangular cross section may be shaped bymachining to round off two adjacent corners so that when viewed from oneend, half of the bar has a semicircular cross section with no cornersand the other half has two of the original 90° corners. It is therounded part of the bar that provides the arcuate surface.

If desired, temperature sensors may be employed in the support memberitself and/or adjacent to the heating source to ensure that sufficientheat energy is applied to raise the temperature of the seam area abovethe glass transition temperature of the thermoplastic polymer in uppercoatings, such as in the charge transport layer of photoreceptors, whileavoiding undue heating of the support member.

A typical temperature range for heat treating a flexible photoreceptorbelt containing a polycarbonate, with dissolved or molecularly dispersedcharge transport compound, charge transport layer having a thickness ofabout 24 micrometers is between about 180° F. (82° C.) and about 206° F.(97° C.). Cooling of the heat treated seam may be conducted in ambientair with much of the heat being absorbed by the supporting member. Othercooling methods could be used such as chilled water in the supportingtube or cold air blowing onto the material. Generally, the traversing,heating and quenching of a seam are accomplished within about 3 andabout 15 seconds with the process of this invention for belts having awidth of between about 20 centimeters and about 60 centimeters.

Thus, the process and apparatus of this invention provides a belt inwhich seam bending stress during dynamic flexing over the rollers of abelt support module is eliminated during image cycling. This stressrelease in the seam prevents premature seam cracking and delamination inthe welded seam area as a belt is cycled over belt module supportrollers. It is important to note that after the heat treatment of thisinvention, cracking has never been seen to be a problem when the seamarea is under compression as it cycles through any straight, flat runsbetween roller supports in an imaging system.

A number of examples are set fort hereinbelow and are illustrative ofdifferent compositions and conditions that can be utilized in practicingthe invention. All proportions are by weight unless otherwise indicated.It will be apparent, however, that the invention can be practiced withmany types of compositions and can have many different uses inaccordance with the disclosure above and pointed out hereinafter.

EXAMPLE I

An electrophotographic imaging member web was prepared by providing aroll of titanium coated biaxially oriented thermoplastic polyester(Melinex, available from ICI Americas Inc.) substrate having a thicknessof 3 mils (76.2 micrometers) and applying thereto, using a gravureapplicator, a solution containing 50 parts by weight3-aminopropyltriethoxysilane, 50.2 parts by weight distilled water, 15parts by weight acetic, 684.8 parts by weight of 200 proof denaturedalcohol, and 200 parts by weight heptane. This layer was then dried to amaximum temperature of 290° F. (143.3° C.) in a forced air oven. Theresulting blocking layer had a dry thickness of 0.05 micrometer.

An adhesive interface layer was then prepared by applying to theblocking layer a wet coating containing 5 percent by weight, based onthe total weight of the solution, of polyester adhesive (Mor-Ester49,000, available from Morton International, Inc.) in a 70:30 volumeratio mixture of tetrahydrofuran/cyclohexanone. The adhesive interfacelayer was dried to a maximum temperature of 275° F. (135° C.) in aforced air oven. The resulting adhesive interface layer had a drythickness of 0.07 micrometer.

The adhesive interface layer was thereafter coated with aphotogenerating layer containing 7.5 percent by volume trigonalselenium, 25 percent by volumeN,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine, and67.5 percent by volume polyvinylcarbazole. This photogenerating layerwas prepared by introducing 160 gms polyvinylcarbazole and 2,800 mls ofa 1:1 volume ratio of a mixture of tetrahydrofuran and toluene into a400 oz. amber bottle. To this solution was added 160 gms of trigonalselenium and 20,000 gms of 1/8 inch (3.2 millimeters) diameter stainlesssteel shot. This mixture was then placed on a ball mill for 72 to 96hours. Subsequently, 500 gms of the resulting slurry were added to asolution of 36 gms of polyvinylcarbazole and 20 gms ofN,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'- biphenyl-4,4'-diaminedissolved in 750 mls of 1:1 volume ratio of tetrahydrofuran/toluene.This slurry was then placed on a shaker for 10 minutes. The resultingslurry was thereafter applied to the adhesive interface by extrusioncoating to form a layer having a wet thickness of 0.5 mil (12.7micrometers). However, a strip about 3 mm wide along one edge of thecoating web, having the blocking layer and adhesive layer, wasdeliberately left uncoated by any of the photogenerating layer materialto facilitate adequate electrical contact by the ground strip layer thatis applied later. This photogenerating layer was dried to a maximumtemperature of 280° F. (138° C.) in a forced air oven to form a drythickness photogenerating layer having a thickness of 2.0 micrometers.

This coated imaging member web was simultaneously overcoated with acharge transport layer and a ground strip layer by co-extrusion of thecoating materials. The charge transport layer was prepared byintroducing into an amber glass bottle in a weight ration of 1:1N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine andMakrolon 5705, a polycarbonate resin having a molecular weight of about120,000 commercially available from Farbensabricken Bayer A. G. Theresulting mixture was dissolved to give 15 percent by weight solid inmethylene chloride. This solution was applied on the photogeneratorlayer by extrusion to form a coating which upon drying gave a thicknessof 24 micrometers.

The strip, about 3 mm wide, of the adhesive layer left uncoated by thephotogenerator layer, was coated with a ground strip layer during theco-extrusion process. The ground strip layer coating mixture wasprepared by combining 23.81 gms. of polycarbonate resin (Makrolon 5705,7.87 percent by total weight solids, available from Bayer A. G.), and332 gms of methylene chloride in a carboy container. The container wascovered tightly and placed on a roll mill for about 24 hours until thepolycarbonate was dissolved in the methylene chloride. The resultingsolution was mixed for 15-30 minutes with about 93,89 gms of graphitedispersion (12.3 percent by weight solids) of 9.41 parts by weightgraphite, 2.87 parts by weight ethyl cellulose and 87.7 parts by weightsolvent (Acheson Graphite dispersion RW22790, available from AchesonColloids Company) with the aid of a high shear blade dispersed in awater cooled, jacketed container to prevent the dispersion fromoverheating and losing solvent. The resulting dispersion was thenfiltered and the viscosity was adjusted with the aid of methylenechloride. This ground strip layer coating mixture was then applied, byco-extrusion with the charge transport layer, to the electrophotographicimaging member web to form an electrically conductive ground strip layerhaving a dried thickness of about 14 micrometers.

The resulting imaging member web containing all of the above layers wasthen passed through a maximum temperature zone of 240° F. (116° C.) in aforced air oven to simultaneously dry both the charge transport layerand the ground strip.

An anti-curl coating was prepared by combining 88.2 gms of polycarbonateresin (Makrolon 5705, available from Goodyear Tire and Rubber Company)and 900.7 gms of methylene chloride in a carboy container to form acoating solution containing 8.9 percent solids. The container wascovered tightly and placed on a roll mill for about 24 hours until thepolycarbonate and polyester were dissolved in the methylene chloride.4.5 gms of silane treated microcrystalline silica was dispersed in theresulting solution with a high shear dispersion to form the anti-curlcoating solution. The anti-curl coating solution was then applied to therear surface (side opposite the photogenerator layer and chargetransport layer) of the electrophotographic imaging member web byextrusion coating and dried to a maximum temperature of 220° F. (104°C.) in a forced air oven to produce a dried coating layer having athickness of 13.5 micrometers.

EXAMPLE II

The electrophotographic imaging member web of Example I having a widthof 353 millimeters, was cut into 4 separate rectangular sheets ofprecise 559.5 millimeters in length. The opposite ends of each imagingmember were overlapped 1 mm and joined by ultrasonic energy seam weldingprocess using a 40 Khz horn frequency to form 4 seamedelectrophotographic imaging member belts. Three of these seamed beltsare to be subjected to a seam stress release heat treatment processwhile the remaining untreated one is used to serve as a control.

Comparative Example III

One of the welded electrophotographic imaging member belts described inExample II was suspended over a horizontally positioned cylindrical backsupporting aluminum tube, having a 2-inch (5.08 centimeters) diameter, awall thickness of about 1/4 inch (6.35 millimeters), and an anodizedouter surface, with the welded seam parked directly along the top (i.e.12 o'clock position) of the back support cylindrical tube. Anothercylindrical aluminum tube identical to the back supporting cylindricaltube was inserted inside the hanging belt loop so that the tube hangs atthe bottom of the loop to ensure conformance of the welded seam to theouter arcuate upper surface of the back supporting cylindrical tube andto provide a 180° wrap angle for the seam area as illustrated in FIG. 5.The temperature of the seam area was raised to about 90° C., 8° C. abovethe glass transition temperature (Tg) of the charge transport layer,using a hot air impingement technique to represent the prior art heattreatment approach.

Observation with an infrared sensing camera showed that the seam heattreatment process required over 1 minute to reach the desired seam areatemperature for softening of the charge transport layer in the seam areato effect seam stress release. Since the supplied heat energy was alsobeing conducted through the belt to the back supporting cylindricaltube, it was noted that the resulting heated seam area required about11/2 minutes of cooling time for the seam to return to ambient roomtemperature. It was also noted that the prior art seam heat treatmentmethod, if continued for a plurality of belts, could cause a substantialrise in room ambient temperature.

The seam area receiving the heat treatment had a width of about 2 inchesover both sides of the seam (i.e. extending a perpendicular distance of1 inch from the centerline of the seam) and was found to exhibit asubstantial amount of imaging member set (i.e. when viewing the seamarea from one end of the seam of a belt resting on a flat table top, thetreated seam area exhibited a pronounced curve resembling the curvatureof the back supporting cylindrical tube).

EXAMPLE IV

The second seamed electrophotographic imaging member belt of Example IIwas mounted onto the back supporting cylinder for seam heat treatmentprocessing according to the procedure described in Example III, exceptthat the heat source used was a sealed carbon dioxide laser heatingsource (Model Diamond 64, available from Coherent, Inc.). The treatmentprocessing used an arrangement similar to the schematic illustrationshown in FIG. 6. This carbon dioxide laser heating source had a 150wattage power capability, but for the present seam heat treatmentpurpose, it was adjusted to deliver an energy output of only 5 watts ata 6 millimeter diameter of raw laser beam spot. An infrared sensingcamera was employed to adjust the laser delivery of 150 hertz frequency,50 microseconds pulse duration, and a seam traversing speed of 2 inchesper second (5.08 centimeters per second) to ensure that the seamtreatment area temperature was 90° C. which was sufficient to soften thecharge transport layer in the seam area to effect seam stress release.The temperature was not so high that it caused problems such asexcessive charge transport layer flow, burning of the layers and/orexcessive heating of the support tube. The seam area of the imagingmember belt was placed on a horizontally movable cantilevered hollowanodized aluminum tube having a 1/4 inch (6.4 millimeters) wallthickness, the seam being positioned on the tube in the 12 o'clockposition with the seam being parallel to the axis of the tube. The tubecontained a pair of slots, one slot at the 9 o'clock position and theother at the 3 o'clock position. Each slot extended along the length ofthe imaging belt width and was 2 millimeters wide. The free end of thetube was sealed by a cap and the supported end was connected to aflexible hose leading through a valve to a vacuum source. The vacuumsource was maintained at a pressure of about 40 mm Hg. The belt in theseam area was held down against the upper surface of the tube when thevalve to the vacuum source was opened so that the seam area conformed tothe shape of the upper surface of the tube.

The heat source emitted a dominant radiant wavelength of 10.64micrometers and a substantially circular laser spot of about 6 mm indiameter incident over the seam area for instant seam heating andsubsequent quick cooling as the entire width of the imaging member beltand length of the seam was moved under the heat source. At a seamtraversal speed of 2 inches (5 centimeters) per second, the entire seamstress release heat treatment process was completed in about sevenseconds and the resulting 6 mm width treated seam area did not exhibit aseam area set like that observed in the prior art seam treatment processdemonstrated in Comparative Example III.

EXAMPLE V

The third seamed electrophotographic imaging belt of Example II wassubjected to the same carbon dioxide laser seam heat treatment processaccording to the procedures described in Example IV, with the exceptionthat a zinc selenide lens was used to defocus the laser beam in order togive a 15 millimeter diameter incident laser spot on the seam area toeffect the heat treatment process. The laser frequency used was 150hertz, the pulse duration was 115 microseconds, and the relativetraversal speed between the stationary spot and moving seam area wit thebelt support cylindrical member was 2 inches per second (5.08centimeters per second).

EXAMPLE VI

The control electrophotographic imaging member belt, the prior artelectrophotographic imaging member belt, and the electrophotographicimaging member belts of the present invention as exemplified by ExampleII, Comparative Example III, Example IV, and Example V, respectively,were each dynamically cycled and print tested in a xerographic machine,having a belt support module comprising a 25.24 mm diameter driveroller, a 25.24 mm diameter stripper roller, and a 29.48 mm diametertension roller to exert a belt tension of 1.1 pounds per inch. The beltcycling speed was set at 65 prints per minute.

The control non-heat treated belt of Example II was cyclic tested toonly about 56,000 prints because the testing had to be terminated due topremature seam cracking/delamination problems.

Although the prior art belt of Comparative Example III, with a 21/2 inch(6.25 centimeters) wide heat treated seam, area cycled to 250,000 printswithout exhibiting any evidence of seam failure, the appearance ofripples was observed, the ripples having a 500 micrometers peak-to-peakheight and a periodicity of about 35 mm in the imaging zones adjacent tothe seam heat treatment area after only 40 prints. These ripples causedcopy print-out defects during xerographic imaging. Moreover, the largeset in the seam heat treat area formed a 0.5 mm surface hump thatinteracted with a cleaning blade operation thereby impacting thecleaning efficiency of the blade. When measured for dimensionalintegrity, the seam heat treatment process of Comparative Example IIIwas found to cause a 0.05 percent circumferential belt shrinkage.

When the same belt cycling procedure is repeated with the belt of thepresent invention (the imaging member of Examples IV and V), no seamfailure was observed after 250,000 prints for each laser treated belt.However, in an apparent contrast to the prior art seam heat treatment,the seam stress release heat treatment process of the present inventiondid not exhibit a belt seam area surface protrusion caused by any set.Moreover, the belt of this invention had no notable ripple appearance inthe image zones. Further, the belt of this invention exhibitednegligible belt treatment induced belt circumference shrinkage.

In summary, the seam heat stress release process of the presentinvention resolves seam cracking/delamination problems, provides a veryshort treatment processing cycle time, avoids seam area heat induced setproblems, prevents the appearance of ripples in the imaging zonesadjacent to the seam heat treatment area, and produces a dimensionallystable imaging member belt. These results demonstrate clear advantage ofthe process of this invention over those used by the prior art seam heattreatment processes.

Although the invention has been described with reference to specificpreferred embodiments, it is not intended to be limited thereto, ratherthose having ordinary skill in the art will recognize that variationsand modifications may be made therein which are within the spirit of theinvention and within the scope of the claims.

What is claimed is:
 1. A process for treating a seamed flexibleelectrostatographic imaging belt comprisingproviding an imaging belthaving two parallel edges, the belt comprisingat least one layercomprising a thermoplastic polymer matrix and a welded seam extendingfrom one edge of the belt to the other, the seam having an imaginarycenterline, providing an elongated support member having at arcuatesupporting surface and mass, the arcuate surface having at least asubstantially semicircular cross section having a radius of curvature ofbetween about 9.5 millimeters and about 50 millimeters, supporting theseam on the arcuate surface with the region of the belt adjacent eachside of the seam conforming to the arcuate supporting surface of thesupport member, precisely traversing the length of the seam from oneedge of the belt to the other with thermal energy radiation having anarrow Gaussian wavelength distribution of between about 10.4micrometers and about 11.2 micrometers emitted from a carbon dioxidelaser, the thermal energy radiation forming a spot straddling the seamduring traverse, the spot having a width of between about 3 millimetersand about 25 millimeters measured in a direction perpendicular to theimaginary centerline of the seam to substantially instantaneously heatthe thermoplastic polymer matrix in the seam and the region of the beltadjacent each side of the seam directly under the heating spot tobetween the glass transition temperature of the polymer matrix and atemperature about 25° C. greater than the glass transition temperatureof the polymer matrix, and rapidly quenching the seam by thermalconduction of heat from the seam to the mass of the support member to atemperature below the glass transition temperature of the polymer matrixwhile the region of the belt adjacent each side of the seam conforms tothe arcuate supporting surface of the support member.
 2. A processaccording to claim 1 including supporting the seam on the arcuatesurface with the region of the belt adjacent each side of the seamconforming to the arcuate supporting surface of the support member withbetween about 10° and about 180° of wrap.
 3. A process according toclaim 1 including completing the traversing, heating, and quenchingwithin about 3 and about 15 seconds.
 4. A process according to claim 1wherein the carbon dioxide laser thermal energy radiation has a powerdensity of from about 0.01 watt per square millimeter to about 0.71 wattper square millimeter.
 5. A process according to claim 4 wherein thecarbon dioxide laser thermal energy radiation has a frequency range fromabout 50 hertz to about 200 hertz.
 6. A process according to claim 1wherein the carbon dioxide laser is a sealed carbon dioxide laser.
 7. Aprocess according to claim 1 including defocusing with a lens thethermal energy radiation from the dioxide laser.
 8. A process accordingto claim 7 wherein the lens is a zinc selenide lens.
 9. A processaccording to claim 1 including traversing the seam from one edge of thebelt to the other with thermal energy radiation by moving the seam whilemaintaining the laser stationary.
 10. A process according to claim 9including traversing the seam from one edge of the belt to the other ata speed between about 2.54 centimeters and about 12.7 centimeters persecond.
 11. A process according to claim 1 wherein the thermal energyradiation from the laser has a circular cross section.
 12. A processaccording to claim 1 wherein the electrostatographic imaging belt is anelectrophotographic imaging belt comprising a charge generating layerand a charge transport layer and the layer comprising the thermoplasticpolymer matrix is the charge transport layer.
 13. A process according toclaim 12 wherein the thermoplastic polymer matrix in the chargetransport layer is polycarbonate resin containing dissolved ormolecularly dispersed small charge transport molecules.
 14. A processaccording to claim 1 wherein the electrostatographic imaging belt is anelectrographic imaging belt comprising a supporting substrate layer anda dielectric imaging layer, the dielectric imaging layer comprising thethermoplastic polymer matrix.
 15. A process according to claim 1 whereinthe electrostatographic imaging belt is an intermediate transfer beltcomprising a supporting substrate layer and an imaging layer, theimaging layer comprising the thermoplastic polymer matrix.